Mass spectrometery is one of the leading chemical analysis tools. A mass spectrometer, often used as a detector in conjunction with another instrument (e.g., a gas chromotograph), may be capable of determining the relative abundances of the chemical species present in a gaseous sample by separating the species by atomic mass.
Mass spectrometry is widely used across many disciplines. Mass spectrometers have been sent aboard unmanned spacecraft; both of the Viking landers carried gas chromotograph/mass spectrometer (GCMS) packages, and the Cassini-Huygens probe dropped into Titan's atmosphere carried a GCMS as well. Mass spectrometers are heavily used in the biological sciences; they are one of the commonly used methods of determining protein structure and sequence.
In the medical field of pharmacokinetics, mass spectrometry has been used to track extremely small quantities of drugs through the human body.
Mass spectrometers have been designed for chemical and biological defense; the Block II chemical biological mass spectrometer (CBMS) was designed to be a portable, vehicle mounted instrument capable of detecting chemical and biological threats (e.g., nerve agents, bacteria) in the field. More recently, mass spectrometers have been carried aboard unmanned submersibles to aid in the tracking of hydrocarbons released by the Macondo oil well failure in the Gulf of Mexico on Apr. 20, 2010.
Many other fields have employed mass spectrometry as well. As early as 1976, a mass spectrometer was used to continuously analyze the respired gases of patients on ventilators in intensive care for potentially dangerous complications.